The objective is to obtain new information on the structure and function of fibrinogen. The primary structure of the disulfide containing peptides from CNBr treated fibrinogen is studied because these regions are crucial for the precise holding of the chains. The structure of the N-DSK, containing 11 out of the 28 disulfides in fibrinogen, is completed; the other disulfide fragments are under investigation. Sequencing of the chains of plasmic Fragment D and of overlapping peptides (CNRr derived) between Fragments D and E will allow further elucidation of the primary structure of fibrinogen. The domains in fibrinogen involved in the fibrin formation are being investigated by studying the binding of chemically and enzymatically derived fragments of fibrinogen to insolubilized fibrin monomer, activated N-DSK and Fragment D, respectively. The specificity of thrombin and thrombin-like enzymes is investigated. The molecular mechanism associated with release of Fibrinopeptides A and B will be explored. Platelet-fibrin(ogen) interaction will be studied with several different approaches - including affinity methods. Degradation of fibrinogen in blood circulation is studied with the use of different radioimmunoassay methods for fragments of the molecule.